Stool DNA test for colon cancer not yet cost-effective

NEW YORK (Reuters Health) - The inexpensive stool tests commonly used to screen for colon cancer can be more effective, and much less costly, than newer tests that look for certain genetic markers in the stool, according to a study published Monday.

The findings, say researchers, indicate that the price of stool DNA testing needs to fall considerably before it can be considered a cost-effective way to screen for colon cancer -- or win reimbursement from Medicare, the government health insurance program for the elderly and disabled.

In general, experts recommend that adults at average risk of colon cancer start routine screening at the age of 50, through any of several standard tests or a combination of tests.

FOBT detects hidden blood in the stool, which can be a sign of colon cancer or pre-cancerous growths called polyps. Positive results on the screen prompt a follow-up colonoscopy. FOBT, which involves taking stool specimens at home and mailing them to the doctor's office or medical lab, is simple and cheap, and advances in the tests in recent years have increased their sensitivity.

Stool DNA testing, a newer technology, detects certain genetic markers that may signal cancer; as with FOBT, a suspicious result has to be followed up with a colonoscopy.

Currently, the U.S. Preventive Services Task Force does not include stool DNA testing in its list of recommended tests for routine colon cancer screening, and Medicare does not cover it. Some private insurers do, however.

The new study, published in the Annals of Internal Medicine, was done at the request of Medicare officials to estimate the cost-effectiveness of the DNA tests against that of currently covered tests.

Using data from the medical literature, the researchers estimated that stool DNA testing every three to five years would be about as effective at preventing colon cancer deaths as one commonly used FOBT test (Hemoccult II) performed annually.

The DNA test would be less effective, however, than a more sensitive FOBT called Hemoccult-SENSA, as well as a newer method for detecting blood in the feces called immunochemical fecal occult blood testing (iFOBT).

In the absence of any screening, 57 of every 1,000 65-year-old adults would eventually be diagnosed with colon cancer, estimate the researchers, led by Dr. Iris Lansdorp-Vogelaar of Erasmus Medical Center in Rotterdam, the Netherlands.

Colonoscopy screening every 10 years would be the most effective way to trim that number, according to the researchers. Colonoscopy, which allows a visual inspection of the entire colon, can help prevent colon cancer by allowing doctors to spot and remove polyps.

If there were 100-percent compliance with colonoscopy screening, Lansdorp-Vogelaar and her colleagues estimate, 27 out of every 1,000 65-year-olds would be diagnosed with colon cancer in their lifetime. Moreover, they estimate that 10 per 1,000 would die of the disease -- versus 27 with no screening at all.

With stool DNA testing every three years, 37 of every 1,000 65-year-olds would eventually develop colon cancer, and 13 would die. With Hemoccult-SENSA, the more sensitive FOBT analyzed in the study, those figures would be 32 and 10, respectively, according to the researchers.

The iFOBT approach appeared similar in effectiveness to Hemoccult-SENSA.

When it came to costs, the differences were clear. In 2007, Medicare reimbursed FOBT at $5 per test and iFOBT at $22; in contrast, private insurers typically paid $350 for stool DNA testing.

In an email, Lansdorp-Vogelaar told Reuters Health that the costs of stool DNA testing need to "come down substantially" before it can be considered cost-effective compared with the established colon cancer screening tactics.

She and her colleagues estimate that the test would need to cost $34 to $51 if done every five years, or between $40 and $60 if done every three years. (One of the issues with stool DNA screening is that it is not yet clear how often it should be done.)

Alternatively, Lansdorp-Vogelaar noted, stool DNA testing could become cost-effective if it enticed many people who otherwise would not opt for colon cancer screening at all. But that would seem unlikely.

The analysis considered only one stool DNA test on the market in 2007, as it was the only one with enough research evidence on its performance, Lansdorp-Vogelaar said.

As DNA testing is further refined, its performance may improve and costs may go down. Lansdorp-Vogelaar noted that the first stool DNA test to come to the market cost $795, whereas one recently introduced version costs $220.

Still, she said, "our study shows that costs need to be reduced substantially more for stool DNA testing to be cost-effective compared to the other recommended tests."